1. Field of the Invention
The present invention relates to a spindle positioning method for enabling a spindle motor to stop at a desired position stably in a shortest possible period of time, by making the best use of the decelerating capability of the spindle motor.
2. Description of the Related Art
In a known method for stopping a rotating spindle motor at a desired position, the motor is first decelerated to a base speed for positioning control during a speed control stage; then, a control mode for the spindle motor is switched from the speed control mode to a position control mode; and a position loop control is carried out using the difference between a commanded stop position and a current position as a position deviation.
In order to shorten the time required for the positioning in the known method, the value of position gain may be increased. If, however, the position gain is increased disregarding the accelerating/decelerating characteristics of the spindle motor, the spindle motor may fail to follow the speed command, causing an undesired overshoot. Conversely, if the value of the position gain during the position loop control is set too small for fear of the occurrence of overshoot, the time required for the positioning will inevitably be prolonged. Thus, it is difficult to prevent overshoot and achieve quick positioning at the same time.